Citations

Abstract Background & Aims: Most GIST harbor oncogenic KIT or PDGFRA mutations, which are in most cases heterozygous. However, most GIST co-express both wild-type KIT and PDGFRA with the mutated KIT or PDGFRA. Signaling mediated by heterodimers of the wild-type receptors contribute to GIST growth even after blocking oncogenic signaling by KIT/PDGFRA inhibitors such as imatinib. Previously we found that crenolanib (CP-868596), a PDGFRA/B tyrosine kinase inhibitor with >100-fold selectivity over other tyrosine kinases including KIT and a potent inhibitor of oncogenic PDGFRA signaling in vitro, inhibited the proliferation of KIT+PDGFRA+PDGFRB− GIST-T1 cells with a potency comparable to that of imatinib (IC50: 5.3 nM; imatinib: IC50: 3.5 nM) but had very little effect in the KITlow/−PDGFRAlow/−PDGFRB+ GIST48B cells (maximum inhibition: <50%; IC50>75 nM) and in mouse stem cells for interstitial cells of Cajal (ICC-SC), a presumed cellular source for GIST, which share a phenotype with GIST48B cells (IC50 >600 nM; Hayashi et al., Gastroenterology 2012; 142:S30). Here we investigated whether the antiproliferative effect of crenolanib was dependent on KIT expression, and studied crenolanib's effect on KIT/PDGFRA signaling and on the stability of ETV1, a transcription factor required for GIST growth and survival. Methods: Protein expression and phosphorylation were studied by Western blotting. KITlow/−PDGFRAlow/+PDGFRB+ murine ICC-SC (2xSCS2F10) were retrovirally transduced to express wild-type murine KIT. Cell proliferation was studied by methyl-tetrazolium salt assay. Results: Expression of wild-type KIT in retrovirally transduced ICC-SC dramatically reduced crenolanib's IC50 from 1157 nM to 121 nM. In GIST-T1 cells, crenolanib significantly reduced PDGFRA and KIT protein expression, inhibited PDGFRA phosphorylation (IC50: 5 nM) but had no effect on KIT phosphorylation. Crenolanib applied at 8.3 nM concentration rapidly and profoundly inhibited phosphorylation of ERK1/2 MAP kinases and reduced ETV1 protein levels by >50% in 2 h. The MEK inhibitor PD98059 (50 μM) reproduced crenolanib's effect on ETV1 protein levels with an identical time-course. The inhibitory effects of both crenolanib and PD98059 on ETV1 protein expression could be reversed with the proteasome inhibitor MG132 (10 μM) and accentuated with the protein synthesis inhibitor cycloheximide (10 μg/mL). ETV1 was undetectable in the crenolanib-resistant, KITlow/−PDGFRAlow/−PDGFRB+ GIST48B cells. Conclusions: In KIT mutant, KIT+PDGFRA+PDGFRB− GIST cells, crenolanib induced ETV1 protein degradation by suppressing PDGFRA-dependent MAPK phosphorylation. Crenolanib's antiproliferative effect in these cells may depend on KIT-induced ETV1 expression and reflect the destabilization of ETV1. Grant support: NIH DK58185. Citation Format: Yujiro Hayashi, Michael R. Bardsley, Yoshitaka Toyomasu, Takahiro Taguchi, Brian P. Rubin, Monique Carter, Abhijit Ramachandran, Tamas Ordog. Crenolanib, a highly selective platelet-derived growth factor receptor α/β (PDGFRA/B) tyrosine kinase inhibitor, destabilizes ETV1 protein in KIT-mutant gastrointestinal stromal tumor (GIST) cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1035. doi:10.1158/1538-7445.AM2013-1035

Abstract Background: Occupational stress in resident physicians has profound implications for wellness, professionalism, and patient care. This observational pilot trial measured psychological and physiological stress biomarkers before, during, and after the start of anesthesia residency. Methods: Eighteen physician interns scheduled to begin anesthesia residency were recruited for evaluation at three time points: baseline (collected remotely before residency in June 2013); first-month visit 1 (July); and follow-up visit 2 (residency months 3 to 5, September–November). Validated scales were used to measure stress, anxiety, resilience, and wellness at all three time points. During visits 1 and 2, the authors measured resting heart-rate variability, responses to laboratory mental stress (hemodynamic, catecholamine, cortisol, and interleukin-6), and chronic stress indices (C-reactive protein, 24-h ambulatory heart rate and blood pressure, 24-h urinary cortisol and catecholamines, overnight heart-rate variability). Results: Thirteen interns agreed to participate (72% enrollment). There were seven men and six women, aged 27 to 33 yr. The mean ± SD of all study variables are reported. Conclusion: The novelty of this report is the prospective design in a defined cohort of residents newly exposed to the similar occupational stress of the operating environment. Because of the paucity of literature specific to the measures and stress conditions in this investigation, no data were available to generate a priori definition of primary outcomes and a data analytic plan. These findings will allow power analysis for future design of trials examining occupational stress and stress-reducing interventions. Given the importance of physician burnout in our country, the impact of chronic stress on resident wellness requires further study.

Controlling meal-related glucose excursions continues to be a therapeutic challenge in diabetes mellitus. Mechanistic reasons for this need to be understood better to develop appropriate therapies. To investigate delayed gastric emptying effects on postprandial glucose turnover, insulin sensitivity, and β-cell responsivity and function, as a feasibility study prior to studying patients with type 1 diabetes, we used the triple tracer technique C-peptide and oral minimal model approach in healthy subjects. A single dose of 30 μg of pramlintide administered at the start of a mixed meal was used to delay gastric emptying rates. With delayed gastric emptying rates, peak rate of meal glucose appearance was delayed, and rate of endogenous glucose production (EGP) was lower. C-peptide and oral minimal models enabled the assessments of β-cell function, insulin sensitivity, and β-cell responsivity simultaneously. Delayed gastric emptying induced by pramlintide improved total insulin sensitivity and decreased total β-cell responsivity. However, β-cell function as measured by total disposition index did not change. The improved whole body insulin sensitivity coupled with lower rate of appearance of EGP with delayed gastric emptying provides experimental proof of the importance of evaluating pramlintide in artificial endocrine pancreas approaches to reduce postprandial blood glucose variability in patients with type 1 diabetes.

Key Points Tac/Sir prophylaxis provides equivalent GVHD-free survival when compared with Tac/Mtx in MRD transplantation. Tac/Sir is associated with more rapid engraftment and reduced oropharyngeal mucositis after MRD transplantation.

To provide an understanding of both the preclinical and clinical aspects of closed-loop artificial pancreas systems, we provide a discussion of this topic as part of this two-part Bench to Clinic narrative. Here, the Bench narrative provides an in-depth understanding of insulin-glucose-glucagon physiology in conditions that mimic the free-living situation to the extent possible in type 1 diabetes that will help refine and improve future closed-loop system algorithms. In the Clinic narrative, Doyle and colleagues compare and evaluate technology used in current closed-loop studies to gain further momentum toward outpatient trials and eventual approval for widespread use.

ABSTRACTIntroductionThe Cl. NPhys Trial 3 showed that attributes of nerve conduction (NC) were without significant intraobserver differences, although there were significant interobserver differences. Methods: Trial 4 tested whether use of written instructions and pretrial agreement on techniques and use of standard reference values, diagnostic percentile values, or broader categorization of abnormality could reduce significant interobserver disagreement and improve agreement among clinical neurophysiologists. Results: The Trial 4 modifications markedly decreased, but did not eliminate, significant interobserver differences of measured attributes of NC. Use of standard reference values and defined percentile values of abnormality decreased interobserver disagreement and improved agreement of judgment of abnormality among evaluators. Therefore, the same clinical neurophysiologist should perform repeat NCs of therapeutic trial patients. Conclusions: Differences in interobserver judgment of abnormality decrease with use of common standard reference values and a defined percentile level of abnormality, providing a rationale for their use in therapeutic trials and medical practice. Muscle Nerve 50: 900–908, 2014